When running an Automation process that sends emails, some clients are receiving multiple copies of the email.
A possible cause is that for the clients that are selected for the Automation Process (by the Filter or the View in the Filter of the Process) there are clients where the client email address is the same.
Check the Filter or the View in the Filter that is being used in the Process and ensure that no email addresses are listed against multiple clients.
For Client Groups that contain multiple clients with the same email address, you can use the Primary Client indicator in the view so that, the email is only sent to the Primary Client. Refer to Primary Client in Clients List and, for an example of using this in a Process, refer to Sending a Bulk Email to all Clients.